Since the invention of integrated circuits (ICs), the semiconductor industry has experienced continual rapid growth due to continuous improvements in the integration density of various components (e.g. transistors, diodes, resistors, capacitors, etc.). A significant part of the improvement in integration density comes from repeated reductions in minimum feature size that allow the integration of more components into a given area.
Meanwhile, as semiconductor device features are reduced further, the impacts caused by current-resistance voltage drop (IR drop) effects and electro-migration (EM) effects increase. The IR drop effects refer to the voltage drops along electrical paths resulting from the currents carried by the electrical paths and the resistances of the electrical paths. The EM effects refer to the mass transport of metal due to the momentum transfer between conducting electrons and diffusing metal atoms. The IR drop effects and the EM effects make the performance of an IC deteriorate or even fail.